A variety of human assistance devices provide aid for human motion. Some work tasks and activities demand frequent and heavy lifting or long-term strenuous movement, beyond normal unassisted physical exertion, and can lead to exhaustion and potential injury. In particular, excessive strain on muscles and joints can cause injury to the back, legs, and knees with associated reduction in productivity. The human assistance device as worn by the user is designed to overcome or compensate for the added load or strain and make many work tasks easier to perform.
In one embodiment, the human assistance device uses an exoskeleton with rigid components e.g., linkages and joints, attached to the user's body. The exoskeleton joints are ideally positioned to have an axis of rotation collinear with a natural axis of rotation for adjacent joints. The rigid exoskeleton relies on a framework of linkages connected to the body at select locations via pads and straps to provide the ability to augment human movements that need assistance or otherwise enhance the user's performance, stability, balance, and safety. As the user flexes or extends their limbs, these rigid links move in parallel with the limb, adding considerable inertia to movement. Unfortunately, the rigid exoskeleton also causes considerable restriction to the user's motion that impedes natural and fluid movement.
In another example, U.S. patent publication 2015/0321339 discloses a soft exosuit that generates forces about one or more joints based on anchor elements and connection elements disposed between the anchor elements. The exosuit uses sensors to determine forces on the anchor or connection elements. Actuators are configured to change tension in the soft exosuit in response to the sensors. The exosuit tends to be complex with an overreliance on active components, such as sensors and actuators, to control its operation. The intricate interconnection of anchor elements, connection elements, sensors, and actuators tends to be expensive to manufacture, difficult to configure, slow in response, and overall low reliability.